As it is known that linear α-olefins, such as 1-octene, 1-hexene, etc, are important chemical products and intermediates, they are widely applied in various fields such as comonomers of polyethylene, alcohols plasticizers, flavor additives, synthetic lubricant and additives of oil products. Employing 1-octene and 1-hexene as comonomers will significantly improve the density, and mechanical properties such as tear strength and tensile strength of polyethylene. When be used as alcohols to produce plasticizers, they could endue polyethylene articles better softness at low temperature, processing behavior, better outdoor weathering durability, particularly suitable for wires and cables, automobile accessories, decoration materials, etc.
Even though 1-octene is of great importance in chemical industry, now there is no synthesis technique to produce 1-octene through ethylene oligomerization with high selectivity. In traditional process of ethylene oligomerization, the carbon number of the products is accordant with Schulz-Flory Distribution that results to a lower concentration of 1-octene in the oligomer products. For example, U.S. Pat. No. 6,184,428 discloses a kind of nickel catalyst using boron compound as cocatalyst, which could catalyze ethylene oligomerization to obtain the mixture of linear α-olefins, wherein the amount of 1-octene is 19%. SHOP process (U.S. Pat. Nos. 3,676,523 and 3,635,937) uses a similar catalyst system, and the amount of 1-octene reaches to 11% of oligomer products. Other typical ethylene oligomerization processes, such as Chevron process (DE 1,443,927) of Gulf Research Development Co., and ethylene oligomerization process (BP/Amoco, U.S. Pat. No. 3,906,053) of Ethyl Corp., generally produce 1-octene with concentration of about 13˜25%. Chromium-based catalyst systems are mainly used in trimerization of ethylene, wherein the concentration of 1-octene is low (less than 3%). A iron-based catalyst reported recently (J. Am. Chem. Soc., 1998, 120:7143; Chem Commun. 1998,849; WO 99/02472) for ethylene oligomerization also results to oligomer products with wider distribution, in which the concentration of 1-octene is low (less than 20%) either. According to WO 2004/056478, tetramerization of ethylene produces 1-octene with concentration of no more than 69.3%.